Calibration-curve-based analysis

Garden, J. S., Mitchell, D. G., and Mills, W. N., Nonconstant Variance Regression Techniques for Calibration-Curve-Based Analysis, Anal. Chem. 52, 1980, 2310-2315. 

Garden JS, Mitchell DG, Mills WH (1980) Nonconstant variances regression techniques for calibration-curve-based analysis. Anal Chem 52 2310... 

Two procedures for improving precision in calibration curve-based-analysis are described. A multiple curve procedure is used to compensate for poor mathematical models. A weighted least squares procedure is used to compensate for non-constant variance. Confidence band statistics are used to choose between alternative calibration strategies and to measure precision and dynamic range. 

There are several approaches to minimizing the loss of precision inherent in calibration-curve-based analysis. We have chosen a... 

Method development procedure for calibration-curve-based analysis. (Reproduced with permission from D. 6. Mitchell and J. S. Garden, Talanta, 1982, 29, 921-929, copyright 1982,... 

Equations 10.4 and 10.5, which establish the linear relationship between absorbance and concentration, are known as the Beer-Lambert law, or more commonly, as Beer s law. Calibration curves based on Beer s law are used routinely in quantitative analysis. 

Quantification of Calcium Sulfate Phase Transformations In order to quantitatively describe the progress of phase conversion ratios of absolute intensities of characteristic peaks of each phase s XRD pattern were compared. This method is generally considered suitable for quantitative phase analysis of mixtures [35]. To aid phase quantification, calibration curves based on prepared mixtures with known composition were used and the respective intensity ratios calculated. The intensity ratios were calculated from the intensity of peaks at 26 29.10725.43°, 29.71°/25.43° and... 

Most uses of flow techniques involve the quantitative determination of some target species. This chapter describes various ways of using flow techniques with quantitative purposes, such as calibration curves, based on peak height or peak area, and titrations, based on distance between equivalence points or single-point method. Stopped-flow technique can be used for both, quantitative approach, for example in kinetic methods, or for qualitative determinations inasmuch as it allows spectral and potential scans to be performed. Multiparameter analysis is presented in two forms to be carried out, by multivariate chemometric techniques or by applying sandwich technique. Finally, smart systems are presented as a step forward in automation, commonly used in multiparameter analysis. 

The enzyme-linked immunosorbent assay (ELISA or EIA) is one of the most commonly utilized methods used in protein detection and analysis. An ELISA can provide quantitative information about antigen or antibody concentrations in solution by comparing the results of an unknown sample assay to a calibration curve based on known standard concentrations of the antibody or antigen of interest. Although, there are many variations in how ELISA may be performed, three of the most commonly used representative methods are discussed here (Fig. 1). The choice of which ELISA technique is used often depends on the nature of the antigen or antibody of interest, the availability of appropriate binding pairs, and the specificity of only the antigen of interest to a monoclonal antibody. 

The calibration curve, based on a series of standard copolymers prepared with Relabelled ethylene or propylene, is obtained by plotting the 7.25 absorbance 6.85 absorbance ratio against the C3 weight fraction. The basis for the calibration of many methods for the analysis of ethylene-propylene copolymers is the work published by Natta and co-workers [6], which involves measuring the IR absorption of polymer solntions at 7.25 pm (presumably due to methyl vibrations related to the propylene concentration in the copolymer). In some cases, the dissolution of copolymers with... 

Chemical Limitations to Beer s Law Chemical deviations from Beer s law can occur when the absorbing species is involved in an equilibrium reaction. Consider, as an example, an analysis for the weak acid, HA. To construct a Beer s law calibration curve, several standards containing known total concentrations of HA, Cmt, are prepared and the absorbance of each is measured at the same wavelength. Since HA is a weak acid, it exists in equilibrium with its conjugate weak base, A ... 

The use of hexafluoroisopropanol (HFIP) as an SEC eluent has become popular for the analysis of polyesters and polyamides. Conventional PS/DVB-based SEC columns have been widely used for HFIP applications, although the relatively high polarity of HFIP has led to some practical difficulties (1) the SEC calibration curve can exhibit excessive curvature, (2) polydisperse samples can exhibit dislocations or shoulders on the peaks, and (3) low molecular weight resolution can be lost, causing additive/system peaks to coelute with the low molecular weight tail of the polymer distribution... 

Kinetic methods. These methods of quantitative analysis are based upon the fact that the speed of a given chemical reaction may frequently be increased by the addition of a small amount of a catalyst, and within limits, the rate of the catalysed reaction will be governed by the amount of catalyst present. If a calibration curve is prepared showing variation of reaction rate with amount of catalyst used, then measurement of reaction rate will make it possible to determine how much catalyst has been added in a certain instance. This provides a sensitive method for determining sub-microgram amounts of appropriate substances. 

Concentrations of terbacil and its Metabolites A, B and C are calculated from a calibration curve for each analyte run concurrently with each sample set. The equation of the line based on the peak height of the standard versus nanograms injected is generated by least-squares linear regression analysis performed using Microsoft Excel. 

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